Stabilization of nylon threads and fabrics to sunlight



United States Patent ice STABILIZATION 0F NYLON THREADS AND FABRICS TOSUNLIGHT Joseph M. Kuhn, Haddonfield, Frank A. Sheldon, Magnolia, andMax Silverman, Haddon Heights, N. J., assignors to The Sherwin-WilliamsCompany, Cleveland, Ohio, a corporation of Ohio No Drawing. ApplicationMay 11, 1954, Serial No. 429,106

7 Claims. (Cl. 117-138.5)

properties making them particularly useful as textile materials,nevertheless, they are subject to severe loss in tensile strength uponprolonged exposure to sunlight. The problem is particularly acute wherenylon is used to fabricate window curtain material or automobile seatcovers.

It is a principal object of this invention, therefore, to provide amethod for treating nylon thread either prior to or subsequent toweaving into a textile material or article to render it less susceptibleto the deleterious effects of sunlight, thereby improving the wearcharacteristics of the nylon.

Another object of this invention is to stabilize the tensile strength ofnylon threads, or fabrics made therefrom, to the damaging action ofsunlight.

Other objects of this invention will appear as the description proceeds.

Patented Apr. 30, 1957 Adjustment of the nip of the rolls determines theamount of liquid carried through by the material up to the limit of theability of the material to pick up and retain a liquid. The padding bathis usually prepared as an emulsion, although homogeneous solutionsystems or chemical precipitation means may be used to effect thecoating of the nylon threads with the copper salt. Utilization ofaqueous systems is a very satisfactory way of achieving the desiredresults of this invention because of the ease of handling water basematerials, the avoidance of the fire hazard encountered with solventsystems, the ease of To the accomplishment of the foregoing and relatedends, said invention, then, consists of the means hereinafter fullydescribed and particularly pointed out in the appended claims, thefollowing description setting forth in detail certain illustrativeembodiments of the invention,

such dis-closed means constituting, however, but a few I face with acopper salt of an organic carboxylic acid and curing the coated nylonsurface at a temperature of from about 250 F. to about 500 F. for aperiod of time up to about 10 minutes.

Treatment in accordance with this invention is effected in one ofseveral ways, perhaps the most convenient of which is padding. By thisprocess, the fabric or thread is immersed in a bath containing theactive ingredient removing therefrom an amount sufficient to stabilizethe nylon in the desired manner. Upon leaving the bath the saturatedfabric or thread passes through a restricted passage, as between rolls,whereby excess liquid is removed from the material. In a modification ofthis process, one of a pair of rolls is partially immersed in a paddingbath and as the material being treated passes through the pair of rolls,liquid is carried to the material by the bottom roll, any excess fallingback into the bath.

cleaning equipment after a run or to change the color, etc. It is alsodesirable to employ a resinous material as a binder for the copper saltin the treating compositions.

The threads, or fabrics made therefrom, which are improved with respectto tensile strength stability are those threads and fabrics which aremade from polyamide type resins, e. g., nylon, cit-her dyed or undyed.One form of nylon fabric which is particularly advantageously improvedby the methods and compositions of this invention is nylon marquisette,widely used in the manufacture of window curtains. Other fabrics whichare composed in whole or in part of nylon threads are greatlybeneficiated by the process of this invention.

As previously indicated, the principal active ingredient in the treatingbaths of this invention is a copper salt of an organic carboxylic acid.While there appears to be high selectivity in the metallic ion (certaincobalt salts havealso shown a lesser degree of improvement), the natureof the organic acyl radical is very much less critical. In general, theorganic acidic materials which have been found useful herein contain atleast 6 carbon atoms. No upper limit has been found and even polymericacidic materials may be used to form the copper salts. Apparently itmakes no difference whether the acidic base is aromatic or aliphatic ormixed aromaticaliphatic. The presence or absence of substituent groupsin the molecule also seems to exert little effect; hence halogen,oxygen, etc. may be present as substituent elements.

Specific examples of copper salts which may be used for treating nylonto improve the resistance thereof to loss of tensile strength uponprolonged exposure to sunlight include the copper salt of polyacrylicacid, copper caseinate, copper naphthenate, copper salt or petrex acids(resinous polybasic acids from terpene and maleic anhydride), copperstearate, copper oleate, copper benzoate, copper salicylate, copperphthalate, copper salt of carboxy methyl cellulose acids,copper-8-hydroxy quinolinolate, copper salt of linseed oil fatty acids,etc. Other copper salts which may be used will be evident to thoseskilled in the art.

The treating bath, whether of the emulsion, solvent, or chemicallyprecipitated type, should contain from about 0.1% to about 1.0% byweight of the copper salt.

A typical formulation of a padding bath of the emulsion type is asfollows:

EXAMPLE I Part I: Parts Butylated melamine formaldehyde 50% solids in50-50 xylol-butanol solvent"--- 76 Copper res'inate 24 Part II:

Water 91 Styrene-maleic anhydride condensate 10.5 Morpholine .c 10.5Glyceryl m-onoricinoleate 6.5 Whitening agent (TiOz) 181.5 Part III:

Water 1293.3

Part I is made'by dissolving the copper salt in the xylol-butanolsolution of alkylated -melamine-formaldehyde condensate.

Part H is the emulsifying and suspending system having dispersedthereingif desired, a whitening agent such as rutile titanium dioxide.

Part -I is mixed into Part II, yielding an oil-in-water emulsion whichis a concentrated form of paddingmaterial. This must then be dilutedwith water (Part HI) toyield a suitable padding bath. In general theamount of such diluent (water or solvent) used will be such as toprovide a concentration of copper salt in the final padding bath of fromabout 0.1% to about 1.0%. The above formulation provides a concentrationof copper resinate or 0.18%.

EXAMPLE II sAtypicaLmlvent-type padding-bath is simply a very dilute.solution of the v.coppensalt in a solvent. For.example,,coppernaphthenatemay"he dissolved ina 50-50 xylol-butanol mixture toatconcentration of 0.5% by weight. Any of the available coppersalts oforganic acids dissolved ina .suitablesolvent to a concentration offrornabout 0.1% toahout 1.0% will provide-a suitable padding bath.Obviously a polyamidesolvent will .be avoided.

The solvent ,typecopper saltsolutions may also contain asuitableresinous,.material, such as thealkylatedmelaminerformaldehydecondensates exemplifiedabove in the emulsion type bath. Anyresinousmaterial capable of hardening and adhering to nylon may be used,if desired. lthas been found that resinous materials are not required inthis treatment, but better resistance to laundering is achieved if suchresins are used to bind the copper salt 'to the nylon.

EXAMPLE III Another process of coating the polyamide surface .to protectagainst the deleterious effect of sunlight is by chemical precipitation.Padding equipment is used in this case as in the preceding cases, buttwo baths are involved. The first bath coats the nylon with a watersolution of a reactive organic carboxylic acid salt,-e. g, the ammoniumsalt. This coating is dried and the nylon passed through an aqueoussolution of copper sulphate which causes water insoluble copper salt toform on the nylon surface. Thesurface is then dried and cured asaforesaid.

EXAMPLE IV Another example of an emulsion type-padding bath is "asfollows:

Parts Butylated melamine-formaldehyde condensate 1.6 Ethyl cellulosecps. standard ethoxy) 1.8 Copper stearate 0.4 Xylol 2.2 Emulsifyingagent (ethylene oxide condensate) 1,2 Dibutyl phthalate 0.25 NH4OH 0.15

Water 91.3

This emulsion (oil-in-water type) was used to pad :nylon marquisette ata wet pick-up :of 55%. Stated in another way, each gram of nylonmarquisette fabric on passing through the padder retained 0.55 gram,ofzemulsion. Upon curing, it was observed that thesamplewellowed'slightly. The cause was later found to ,be the :emulsifyingagent. Studies have shown that the amrmonia or morpholine saltsofstyrenewmaleic anhydride condensates are superior emulsifying agentsin that the yellowing tendency is avoided.

Although only trace amounts of copper salt are deposited on thepolyamidefabric, copper stearate-has -a grey-green color and isdesirable, when using on undyed nylon, to employ a whitening agent tomask the color.

A very desirable copper salt from the color standpoint is the coppersalt of a monovinyl benzene-maleic anhydride condensate also used as anemulsifier-thickener. It has a very pale blue color and requires farless whitening to mask its color. Moreover, there appears to be lesstendency to yellowing at curing temperatures. This copper salt is morediflicultto disperse, however.

The monovinyl benzene-maleic co-polymer referred to above isconveniently produced by any one of several established Ways. Theingredients .may be mass polymerized by heating, for example, styreneand maleic anhydride at temperatures between about F. and 300 F. forseveral hours or more. In certain instances it may be found desirable toemploy a small amount, e. g., 0.1% to 1.0% by weight of divinyl benzeneinthe copolymerization reaction. A peroxide catalyst is often used andit is desirablethat the materials be heated with care as by'means of-awater bath. Another method of producing these materials is by conductingthe eo-polymerization in the presence of a solvent forthe startingmaterials and the final product, such as, acctone. Instead of styrene,substituted styrenes including alkylated styrenes, such as, methyl,ethyl, propyl and butyl styrenes, or substituted styrenes,suchagchlorostyrene, or the like may be used'to prepare the co-polymers.Instead of maleic anhydride,there may be used partially esterifiedmaleic acid, such as, the half esters methyl, maleate, ethyl maleate,iso-propyl maleate, sec-butyl maleate, etc. Further discussion of theproduction of these materials may be found by having reference to thepatent to Barrett 2,537,018 dated Jan. 9, 1951; the patent to Seymour,2,533,635 dated December 12, 1950; and the patent to Condo -et 'al.,286,062, dated June 9, 1942. It hasbeen foundthat when using divinylbenzene as a cross-linking agent in these co-polymers, substantiallylarger amounts than those indicated above tend to cause the printingpaste to become too viscous.

.Thus, the form of the bath, or the mode of coating the surface of thepolyamide is not critical, although for convenience and safety reasons,the emulsion system is to be preferred. It is essential to thesatisfactory practice of this invention that thepolyamide surface,Whether as an individual thread .prior to weaving, or in a fabriccornposed.of-.a plurality of threads, or as a wool mass, be coated withacompositioncapable-of depositing a film containing a copper salt of anorganic carboxylic acid of 6 to 22 carbon atoms, and that thethus coatedsurface begheattreated at a temperature of from about 250 F. to about400 F. fora period of time ranging from a few seconds to severalminutes. Quite obviously, the higher curing temperatures will requireshorter curing times, a few seconds, i. e., 10-40 seconds beings quiteetfectiveat 400, F. The converse is also true.

A surprising feature of this invention isthat a,relatively mild heattreatment step is required in order to develop theprotective-qualitiesof the coating on the polyamide surface. Why this is true is not known,.but, as subsequent test data will show, unless thecoated polyamide is'cured,1there .is'no permanent improvement in the tensile strength afterexposure to ultra-violet light.

It is convenient at this point to illustrate the effectiveness :of avariety ,ofthe more common copper salts .for the purposes :of thisinvention by comparing the results obtained from baths containing avariety of concentra- It will be understood-that these be construed aslimiting the invention to the precise scope 'thereof.

Tensile Tensile Curin Ourln No. Active Ingredient Strength StrengthHours Bath 'Iype Time, TempE Before After Exposed Minutes F. ExposureExposure Nona 49. 13 60 Nnnn 49.0 0.5% Cu Salicylate-.-. 49. 7 49. 9 60do 49. 7 22.4 60 0.25% Cu Benzoate.. 50. 2 49.8 60 0.25% Cu Petrexate50. 4 52. 2 60 (in 50.4 25.3 60 0.5% Cu Oaselnate 48. 7 44. 0 60 48. 722.1 60 0.5% Cu Polyacrylate 50. 4 50. 0 60 50. 4 24.0 60 1.0% CuB-hydroxy quinolmolate 48.0 48.4 60 0.5% Cu S-hydroxy qujnoliuolate 48.046.7 60 0.5% Cu PVM/MA 53.0 52. 4 60 53.0 28.4 60 0.5% Cu Stearate 48.840.2 60 do 48. 8 40. 1 100 (in 48.8 32. 9 180 0.6% On Stearate 50. 251.3 117 0.5% Cu Resinate 48.8 48. 2 60 (in 48.8 25. 7 60 0.3% CuResinate 48. 2 47. 1 60 fin 48.2 24.3 60 0.25% Cu Reslnate-- 48. 3 20. 560 0.2% Cu Resinatm..- 49.1 49. 3 60 0.1% Cu Resinate 47. 6 34. 2 60 dn47. 6 16. 5 60 1.0% Go Resinate 49. 2 45. 6 60 0 16% 00 Res at 48.8 24.060 0 16% O0 Resinate (bleached) 48.8 38.7 60 -do 0.5% Cu Reslnate. 49.347. 8 60 Solvent-Resin 0.5% Cu Verseante-- 48.8 48.4 60 Chelate 3-. 33048. 8 22. 5 60 Uneured In determining the data in the preceding table,nylon marquisette fabric pieces 5" x 12" were used. The material wasdipped in the indicated padding bath and passed between rolls allowing awet pick-up of 50-55% of the weight of the dry fabric, i. e., 1 gram ofbath/2 grams of nylon marquisette. Curing was effected in an oven.

The tensile strength measurements were made on the nylon samples in awarp-wise direction only, using the Scott Tensile Strength TestingMachine. The measurement is made by breaking a 4" x 6" specimen between1 x 1" clamps spaced 3" apart. The reading is in pounds. A more detaileddescription of the procedure is contained in Federal SpecificationCCCT-19lb- Method 5100. Unpadded nylon marquisette has a tensilestrength under this method of between 49 and 51 lbs. Nylon marquisettewhich has been heated for three minutes at 330 F. in an oven hassubstantially the same tensile strength and in some cases is even alittle stronger. After 60 hours exposure on a white background, thetensile strength of unpadded nylon runs between and lbs.

In the preceding table, reference has been had to Cu PVM/MA. PVM/MA is aco-polymer of polyvinyl methyl ether and maleic anhydride. In ExamplesXI and XII of Table I, the copper salt of this co-polymer was chemicallyprecipitated on the nylon in the following manner. Ammonium hydroxidewas added in excess to an aqueous solution of the co-polymer ofappropriate concentration (0.5%). This was padded into the nylonmarquisette and air dried. The nylon marquisette was then padded with a0.5% copper salts solution. On a mol per mol basis, there is an excessof copper sulphate over what is needed to react with all of the ammoniumsalt of the co-polymer. The doubly padded nylon marquisette was then airdried, rinsed in cold water to remove the excess copper sulphate andagain air dried.

Examples 29 and 30 refer to copper Versenate. These are copper salts ofethylene diamine tetra-acetic acid. The versenes are sodium salts ofethylene diamine tetra acetic acid and are used as chelating agents forsequestering soluble metallic ions and maintaining them in non-ionicsolution. The pad bath used in Examples 29 and 30 was made by dissolving0.3% trivalent iron versene and 0.2% copper sulphate in water.

The solvent type baths were made by dissolving the designated percentageof copper salt in a 50-50 xylolbutanol solution. Where a solvent-resinbath is indicated,

butylated melamine formaldehyde in a Weight ratio to the copper salt of3:1 was used. Except for the presence of the resinous material, theresin-solvent baths would be the same as the solvent baths.

The chemical precipitation methods for depositing the copper salts onthe nylon were all done in a similar maner. The ammonium salt of theorganic acid was first made by means of aqueous ammonia and applied tothe nylon sample. After drying the fabric was re-padded with a coppersulphate solution of sufficient concentration to contain an excess ofcopper sulphate over that required to precipitate the ammonium salt. Thesample is then rinsed in cold water, dried and cured. The chemicalprecipitation method is generally used where the copper salt isdifficult to disperse in a suitable vehicle.

Exposure to ultra-violet light was carried out in a Fadeometer using thewhite cardboard background. 50 hours of such exposure is equivalent toabout 240 hours exposure without the background.

Table II below compares tensile strengths before and after 60 hoursexposure to ultra-violet light at various curing times and temperatures.The active ingredient in each case was copper resinate applied tocommercial nylon from a 0.5 solution in 50-50 xylol-butanol mixture.

Table II Before After Cure Cure No. Exposure Exposure Time Temp,

seconds F.

Reference has been made above to the use of whitening agents. The reasonsuch agents are used at all is that the polyamide resins have a tendencyto discolor upon heating. Yellowing invariably occurs with untreatednylon marquisette and a bleaching operation is indicated. Any bleachingoperation should be carried out on the alkaline side since solutionshaving a pH below 6 tend to remove the copper salt. Accordingly, it isfrequently desirable to utilize a whitening agent. Good hiding power,high tinctorial power, ready dispersibility, chemical inertness, and lowcost are desirable characteristics of a whitening agent. Titaniumdioxide (rutile) is particularly satisfactory for this purpose althoughzinc oxide and basic lead carbonate may be used. The pigment isdispersed in the padding bath to a concentration of from 2 to about 2-5being suflicient for most purposes.

In another embodiment of this invention the copper salts may be includedin a padding bath for imparting color to nylon. Using from 0.1% to 1% ofacopper salt in a padding bath containing a red pigment, the results inimproved tensile. strength were as noted above for undyed nylon.

It is not mandatory that a resinous material be used as a component ofthe treating bath although the inhibitive effect of the copper salt ispresent only so longas the copper salt is. Thus it is beneficial to usesuch a resinous binder and the most satisfactory are the Water-solubleand water dispersible carbamide-aldehyde resins such asthe urea,thiourea, melamine, etc.-aldehyde condensates. The melamine-formaldehyderesinsand their alkylated analogues have been mentioned above.Urea-formaldehyde resins and thio-urea-aldehyde resins may also be used.

The alkylated melamine formaldehyde condensation products which areuseful in accordance with this invention may be prepared by knownmethods. For example, reference may be had to the patent to-Widmer,2,197,357, and the patent to Swain, Re. 22,402. In general, thesecondensation products are prepared by reacting 2 to 6 mols offormaldehyde with 1 mol of melamine. The condensation product formed isbelieved to be mostly methylol-melamine.

When preparing the various alkylated melamine formaldehyde condensationproducts, it is frequently desirable to prepare first the methylatedmethylol-melamine and then, by an interchange process utilizing analiphatic alcohol of the desired carbon atom content, c. g., 3 to 12carbon atoms, obtain the corresponding alkylated methylol-melamine.Specific examples of such treatment are also given in the patent toJohnstone et a1. Re. 22,566.

Specific examples of the alkylated melamine formalde hyde condensationproducts which may be usedin accordance with this invention includepropylated methylolmelamine, butylated methylol-melamine, hexylatedmethylol-melamine, cyclohexylated methylol-melamine, caprylatedmethylol-melamine, laurylated methylolmelamine, etc.

A preferred material for use in accordance with this invention is thebutylated melamine-formaldehyde product, primarily because of its readyavailability on the market, and for this reason it has been used in thespecific examples which will be understood as merely illustrative of theuse of other such alkylated methylolmelamines.

Other resinous materials may he used including phenolaldehyde resins,oil-modified alkyd resins, etc.

Other. modes of applying the principle of this invention may be employedinstead of those specifically set forth above, changes being made asregards the details herein disclosed, provided the elements set forth inany of the following claims, or the equivalent of such be employed.

2 It is, therefore, particularly pointed out and distinctly claimeda'sthe invention:

1. The method of inhibiting loss of tensile strength in filamentousnylon which comprises coating a nylon surface with a copper salt of anorganic carboxylic acid containing at least6 carbonatomsand curing thecoated nylon surface at a temperature of from about 250 F. to about 500F. for a period of time up to about 10 minutes.

2. The method of claim 1 in which the organic carboxylic acid isanaliphatic carboxylic acid.

3. The method of claim 1 in which the organic carboxylic acid is anaromatic carboxylic acid.

4. The method of claim 1 in which the copper salt is copper resinate.

5. The method of claim 1 in which the copper salt is copper stearate.

6. The method of claim 1 in which the copper salt is copper benzoate.

7. The method of inhibiting loss of tensile strength in nylon fabricwhich comprises saturating said fabric with a padding compositioncontaining from about 0.1% to about by weight of a copper salt of anorganic carboxylic acid containing at least 6 carbon atoms, and curingthe padded nylon fabric at a temperature of from about 250 F. to'about500 F. for a period of time up to about 10 minutes.

References Cited in the file of this patent UNITED STATES PATENTS1,482,416 Snelling Feb. 5, 1924 2,371,884 Gardner Mar. 20, 19452,399,873 Littman et al. May 7, 1946 2,434,913 Dreyfus et a1. Jan. 27,1948 FOREIGN PATENTS 652,947 Great Britain May 2, 1951

1. THE METHOD OF INHIBITING LOSS OF TENSILE STRENGTH IN FILAMENTOUSNYLON WHICH COMPRISES COATING A NYLON SURFACE WITH A COPPER SALT OF ANORGANIC CARBOXYLIC ACID CONTAINING AT LEAST 6 CARBON ATOMS AND CURINGTHE COATED NYLON SURFACE AT A TEMPERATURE OF FROM ABOUT 250*F. TO ABOUT500*F. FOR A PERIOD OF TIME UP TO ABOUT 10 MINUTES.